Insulator



Feb. 28, 1933. JANSSON 1,899,757

INSULATOR Filed Feb. 23, 1926 jlI/BWTOZ".

Patented Feb. 28, 1933 UNITED STATES PATENT OFFICE GUSTAV .7 LU 88011 O! WOIJ-ABTOH, msacnusrrrs, ABSIGHOR TO CONDIT ELECTRICAL IANUFAGIUBIIG OOBPOEATIOH, SOUTH BOSTON, MASSACHUSETTS, A CORPORA- TIOH OI IABSLCHUSRTTS IIBULATOB Application fled Iebrury 8:, 1m. lerlal 10. 89,889.

This invention relates to bushings which are .used to insulate incoming and outgoing high tension leads for electrical apparatus as electric switches, and has particular re erence to bushings of the solid ty wh ch comprises two or more concentric to of msulating material, as porcelain.

In an insulating bushing of the type above set forth, when used with an electric switch,

a massive conducting rod or stud is extended through and is supported by the bushin and bears a contact block at its lower en and, usually, a screw-threaded terminal-com ncctor at its upper end.

- One of the objects of this invention is the provision of means to lock the stud a ainst rotation in and to the bushing, there y to prevent change in alignment between the contact members carried by the lower end of the stud and the movable contact members of the switch.

The conducting stud is adapted to heat and expand when conducting a heavy current. Since the coeflicients of expansion of porcelain and of the stud are much different, and the heating is originated in the stud, it is a further object to connect the stud rigidly with the insulator only at one point, so that the stud is free to expand without applying any material stress to the insulator.

An insulating bushing used for electric switches is subject to substantial pressure and impacts at its lower end, due to the action of the movable contact members, as the switch is operated. With the usual construction of multitube solid bushings the arrangement, and the manner of bonding the tubes together, has been such that the stresses in the tubes, resulting from the operation of the switch, have been largely tension stresses.

Porcelain is relatively weak to resist tensionforces and especially suddenly-applied, or impact, tension forces, and consequently may fail mechanically.

Porcelain, however, is relatively strong to resist compression forces, even though suddenly applied. K

Consequently, a further object of this invention is the provision of a multi-tube bushing so constructed and arranged that the important parts thereof are mainly under compresslon when subjected to the forces and as to facilitate the I this invention is articularly concerned is described but not c aimed in my co-pending application Serial No. 89,888, filed February 23, 1926, which issued as Patent No. 1,816,- 852, dated August 4, 1931.

Fig. 1 is a side elevation partly in section of an electric insulator embodying the invention.

Fig. 2 is a detail illustrating the arrangement of arcing members on the lower end of the insulator of Fig. 1.

As here shown, the insulator embodying my invention includes two concentric porcelain tubes 10 and 12 of substantial length, open at both ends, and spaced apart so as to form an interposed'annular space or compartment 14, which space may be approximately oo-extensive with the length of said outer tube 12 and may have a relatively small cross sectional dimension. Said space may be as crushed porcelain, to improve the specific inductive capacity of said space and reduce losses therein, as set forth in my above named co-pending application.

An annular metal flange 16 is disposed about the outer tube 12 intermediate the ends thereof, and said flange is secured fixedly to said tube by an suitable means, as a body of cement 18. vided in the vertical face of said flange 16 to receive cement whereby to strengthen the bond between said flange and said cement. Said flange is secured by bolts 24 to the casing 22 0 any suitable electrical apparatus as an electric switch.

A body of cement 42 is provided to unite the tubes rigidly together at their lower ends and also to form a bottom closure for the ular grooves 20 are pro-' space 14. The efiectiveness of the cement the tube walls at this point and bond is increased by staggered annular.

grooves 44 formed in the proximate faces of adapted to be occupied by the cement.

V Said inner tube is provided at its lower' end withan enlarged annular recess 28 adapted to receive the metal bushing 30, and a body of cement 32 between the bushing and said inner tube secures said bushing fixedly in position in said tube so that the inner passage of the bushing is aligned withthe axial passage in the tube 10. Said bushing is provided with an integral outstanding annular flange 34 which is adapted to bear against the end of said tube and receive any pressure exerted against the bushing. i

A conductor or stud. 36 is dis osed within the axial assage 38 of said tu e 10 and is screw-three. ed at its lower end into the bushing and is arran ed to extend a substantial distance below the ushing to provide the externally screw-threaded 'portion40. I

Whenthe bushing is employed as the terminal of an electric switch, for which use it is especially adapted, a contact block 41 is screw-threaded onto said portion 40 of the conductor-stud and is provided with the lower contact surface 43 against which the main movable contact member 44 is adapted vto bear. Said block is also provided with the spaced depending arcing members 45.

Saidcontact-block'41 is arranged to be held in fixed relation with the conductor-stud by means of some suitable clamping device, as

v the lock nut 47, which 'is'adapted to secure it from turning on said conductor rod 36 after said fixed contact member is aligned with its cooperating movable contact member.

A metal. furrule-46 is fixed to the upper end of the outer tube 12 by a body of cement 48 or other suitable attaching means, and ex-.

tends over and provides a closure for the top openings of both tubes 10 and 12. Said ferrule is also provided with the integral upstanding neck 50 which is arranged to receive said conductor 36 in the central opening 52 thereof. An axially extended slot 54 provided in said conductor 36 and a corresponding slot 56 in the adjacent neck 50 are adapted to receive a spline 58' whereby to prevent rotation of said conductor within said neck, thus preserving the alignment of the contact block 41 with its cooperating movable switch member. One of said slots, as the slot 54 is arranged to be sufiiciently longer than said spline to permit free vertical, or axial, movement of said conductor.

A yielding packing 60 of suitable insulating material may be interposed between the ferrule 46 and the top of the inner tube 10 to provide a yielding cushion against which said inner tube may expand.

The conductor 36 extends through and beyond the end of the ferrule 46 and is screwthreaded into the metal terminal connector 62. Said connectoris provided with an externally screw-threaded stud 64 to which a line conductor is adapted to be attached, and said connector is also provided with a depending- 10 and 12 are ro- 7 surface leakage path around the end of the insulator. The lower corrugated end of said inner tube is extended belowthe lower end of said outer tube, and is enlarged at its-lower end, whereby to enhance thellength-of the leakage path over the corrugations. Theupper end of said outer tube 12 is a series of petticoat flanges out the major portion of its length, all of provided with 0 extending from its top to the supporting flange 16. It

will be noticed that the inner tubeis p'ractically free from any irregularities throughthe flanges or petticoats being carried by the outer tube 12, so that the manufacture of the inner tubes and the assembly of the insulator is simplified over the usual' insulaf tors of this type.

- By reasonof the bonding of the insulating tubes at their lower ends, a pressure exerted upwardly on the lower end of the inner tube is transmitted through the inner tube to the cement which bonds it to the outer. tube and thence by way of the outer tube to the sup.-

.porting flange of the insulatorthus placing both tubes under compression. Porcelain is relatively stron in compression. By the PI'OVISIODS of thls Invention, any stress acting upwardly against the end of the insula- 7 improvement over the heretofore customary relatively weak under tension, while it is i construction wherein the insulator is subjected to tension stresses, and is stressed throughout its entire length.

The construction may be otherwise modified without departing from the spirit of the invention.

I claim:

I 1. In an electric insulator, the combine-- tion of an outer insulatingtube having a series of integral petticoats, an inner insulating tube having straight tubular walls, coextensive with the length of said outer tube and an enlarged externally corrugated section disposed below the lower end of said outer tube, a metal cap overlying the upper ends of said tubes, and attached to said outer tube only, and an attaching flange connected with said outer tube intermediate its ends.

2. In an insulator,the combination of two concentric tubes of insulating material having an annular space between them, a supporting flange carried by said outer tube intermediate its ends, an axial conductor disposed within the inner tube and rigidly affixed thereto atits lower end only and having its upper end in sliding engagement with the insulator, and a body of cement securing said tubes firmly together at their lower ends only.

3. In an electric insulator, the combination of inner and outer insulating tubes open at both ends and having an intervening ace, a metal cap disposed over the upper en s of said tubes and fixed to said outer tube, an axialconductor disposed within said inner tube and passing through said cap, and a key cooperating between said ca and said conductor to prevent turning 0 said conductor within said tubes while permitting free axial movement through said cap.

4. In an electric insulator, the combination of spaced concentric insulating tubes having means rigidly connecting their lower ends only, an axial conductor isposed within the inner tube, and a metal bushing having an outstanding flange screw-threaded to the end of said conductor and disposed within a recess in. the lower end of and fixed to said inner tube, said flange having a bearing against the end of said inner tube.

5. In an electric insulator, the combination of: two spaced concentric tubes of insulating material havin means rigidly connectin their lower en s, a supportin flange carrie by said outer tube interme iate its ends, a conductor disposed within said inner tube and fixed thereto at its lower end, a metal ferrule disposed over the tops of said tubes to form a closure for the upper ends thereof and secured fixedly to said outer tube, and means connecting said conductor and said metal ferrule to restrain said conductor against rotation while permitting it to move lengthwise therein.

' 6. An electric insulator comprising an insulating tube open at the top, a ferrule carried by the upper end of said tube and providing a cover therefor, said ferrule having an upstanding neck, a conductor passed freely through and arranged for axial movements in said neck due to expansion and contraction, and a cap carried by said conductor having a depending side wall which surrounds said neck and is free to move thereover following movements of said conductor while preserving its surrounding relation with said neck.

7. An insulator having the combination of two insulating tubes, one contained within longitudinal expansion and the other, and having a rigid connection between them at their lower ends only, said tubes being otherwise free from positive connection and being free to expand independently, a relatively rigid conductor extended through said inner tube and having a rigid connection with the insulator only at the lower end of said inner tube, and being otherwise free from rigid connection with the insulator.

8. An insulating bushing includin the combination of an outer insulating she 1, an inner insulating tube, and a rigid conducting stud extended through said insulating tube, said insulating tube having means supporting it in said shell which provides for free longitudinal expansion and contraction thereof and said conducting stud having a support on said inner tube only at its lower end and having a sliding engagement with said bushing at its upper end whereby it can freely expand and contract longitudinally.

9. An insulating bushing includin the combination of an outer insulating she I, an inner insulating tube and a rigid conducting stud extended through said insulating tube, said insulating tube having means supporting it in said shell which provides for free contraction thereof and said conductin stud having a connection with said bushing only at the lower end of said inner insulating tube and being otherwise free from a positive restraining connection with said bushing and having a sliding engagement with said bushing at its up er en whereby said stud is free to expan and contract longitudinally.

10. In an electric insulator, the combination of an outer insulating tube which has a series of petticoats thereon, an inner insulating tube which has a straight tubular wall which lies within and extends lengthwise of said outer tube for at least the major portion of its length and has an enlarged externally-corrugated section which is disposed below and overlies the lower end of said outer tube, a metal cap which overlies the upper ends of said tubes and has a weatherroof connection with said outer tube, an an attaching flange connected with said outer tube intermediate its ends.

11. In an electric insulator, the combination of an outer insulating tube which has a series of petticoats thereon, an inner insulating tube which has a straight tubular wall which lies within and extends lengthwise of said outer tube for at least the major portion of its length and has an enlarged externallycorrugated section which is disposed below and overlies the lower end of said outer tube, a metal cap which overlies the upper ends of said tubes and has a weather-proof connection with said outer tube, an attaching flange connected with said outer tube intermediate its ends, and means securing the lower endsQ of said two tubes in the aforesaid relation.

12. In an electric insulator, the combination of an outer insulating tube which is open at both ends, an inner insulating tube which is open at both ends and has a straight side wall which is located within and overlies the major part of the inner face of said outer tube and has an enlarged lower portion which is located below and overlies the lower end of said outer tube, a metal cap which overlies the upper ends of said tubes and constitutes a closure therefor and has a weather-proof connection with said outer tube, a metal memher which overlies the lower end of said inner tube, and a stud which extends through said tubes and has a connection both with said ca and member.

13. 11 electric insulating bushing consisting of the combination of a straight outer insulating tube having an outstanding metal attaching flange fixed thereto intermediate its ends, a straight inner insulating tube iocated within said outer tube having its upper end terminated below the upper end of said outer tube and its lower end extended downwardly below the lower end of said outer tube and having an enlarged lower end which islocated below and overlies the lower end of said outer tube and a connection with the lower end of said outer tube by which an upward thrust on the lower end of said tube is transmitted to the lower end of said outer tube, a metal cap overlying the upper ends of both tubes and constituting a closure therefor and having a weather-proof connection with the upper end of said outer tube, and a stud extended through said cap and said tubes and having a pressure-bearing on the lower end of said inner tube, the connections between the lower ends of said tubes, and between said stud and the lower end of said inner tube being such that both tubes are placed only in compression between the lower ends thereof and said attaching flange when the lower end of said inner tube is subjected to an upward thrust.

14. An insulating bushing comprising an outer insulating tube having an attaching flange intermediate its ends, an inner insulating tube which is located within said outer tube except at the bottom thereof where it projects below said outer tube and has an enlarged lower end that is too large to pass into said outer tube, a metal cap overlying the top of said outer tube, a bearing member overlying the enlarged lower end of said inner tube, and a conducting stud extended through said inner tube and said metal cap and said bearing member.

15. In an electric insulator, the combination of an insulating tube, a conducting stud disposed within said tube, means located at one end of said tube which rigidly connects one end only of said stud with said end of said tube against axial movement relative to GUSTAV J ANSSON. 

